Childhood adversity is remarkably prevalent and significantly increases the risk of developing psychiatric symptoms during adulthood, especially depression and anxiety. Preclinical studies found that early-life stress induces excessive release of stress hormones which inhibit neuronal growth, particularly in the hippocampus. Recent research from M. Teicher et al. found that young adults with childhood maltreatment have smaller hippocampal subfield volumes compared to age- and education-matched controls that did not have childhood maltreatment. Studies from S. Lazar et al. found that the Mindfulness-Based Stress Reduction (MBSR) program is associated with increased hippocampal gray matter density. With the co-mentorship from Drs. Teicher and Lazar, the objective of the proposed research is to evaluate the effect of MBSR in reducing the depression and anxiety symptoms in young adults with childhood adversity, as well as for inducing hippocampal structural and functional changes. There are three specific aims focused on achieving this objective: (Aim 1): To examine changes in perceived stress and clinical symptoms after MBSR. (Aim 2): To investigate hippocampal structural and functional changes after MBSR, and how they are related to stress reduction and clinical effects. (Aim 3): To analyze changes of hippocampal functional connectivity in the global neural network. This study will improve our understanding about the clinical and neural effects of MBSR for young adults with childhood adversity.